The present invention relates to a milking apparatus, and more particularly to a valve for controlling the flow of milk through a milk pipeline leading from a milking machine to a teat coupling.
In order to shut off a pipeline carrying milk in a milking installation, a valve is used which is provided with an elastic, hose-shaped sealing unit, which can be connected to the milk pipeline, optionally by means of pipe connectors. The sealing unit is arranged in a housing, forming a chamber lying between the sealing unit and the housing. The housing is provided with a connection for a working medium, wherein the connection opens out into the chamber.
A valve of this type is known, for example, from DE 26 58 361 C2 and DD-PS 131 775. The elastic, hose-shaped sealing unit can be brought into a sealing position by means of external over-pressure. The over-pressure is obtained by connecting the chamber to the ambient atmosphere while in the sealing unit the low-pressure of the milk pipeline acts such that the sealing unit is compressed. The sealing security of such a valve is substantially dependent upon the amount of the over-pressure which is produced by a pressure differential between the pressure present in the sealing unit and the ambient pressure, and upon the sealing unit being capable of being deformed.
With the known embodiments, a sufficiently high pressure differential is necessary for secure and reliable sealing of the valve. A high pressure differential such as this can be obtained in that the chamber is exposed to a pressure exceeding normal atmospheric pressure. The installation of a pressure system is necessary for this, whereby expenditure for the installation increases significantly.
The use of a valve is particularly problematic, as described, for example, in DE 26 58 361 C2, when it is used to shut off a long milk hose on a teat cluster. The teat cluster is in contact with the ambient atmosphere after removal from a teat of a cow, so that a very slight low pressure is created by means of atmospheric air flowing in, which is not necessarily sufficient to seal the valve securely.
Furthermore, with such usage, the situation arises where only the outlet side of the valve is under low pressure, wherein the inlet side of the valve and consequently also a part of the sealing unit is at atmospheric pressure. The chamber which is exposed to atmospheric pressure does not necessarily generate, together with the low pressure which is at the outlet side of the sealing unit, a sufficiently high pressure differential to make reliable sealing of the valve possible.
Another valve for a milk pipeline is known from EP 0 075 255 A1. The valve is configured in the form of a diaphragm valve. The diaphragm is formed by a hose. Inside the hose, a core with a figure-of-eight shaped cross-section is arranged at the level of a control chamber surrounding the hose, against which core the inside wall of the hose lies when the pipeline is sealed. Even with this configuration of the valve, a sufficiently high pressure differential is necessary for secure and reliable sealing thereof. The pressure differential necessary for sealing the valve is in particular dependent upon the material properties of the hose.
Proceeding from the above, an object of the present invention is to further develop the known valve such that the valve can be brought into a sealed position reliably even by means of a slight external over-pressure. A further object of the invention is to configure the valve such that it causes relatively small losses of pressure in the line.